Counterbalance and lift system for mowing units

ABSTRACT

Means are provided constituting a single unified system for accomplishing the several functions of counterbalancing, adjusting, equalizing, damping, lifting, and stowing the individual units of a mowing machine or lawnmower. An air charge in an accumulator functions as the resilient counterbalancing element; adjustability is obtained by the alteration of the air pressure; equalization results from hydraulic distribution to lifting cylinders at each of the mowing units; and oscillation is suppressed by damping restrictions in the hydraulic lines. Additionally, a pump and valve combination in the hydraulic line converts the system to lift the moving units for transport and to elevate and stow same.

[ Feb. 15,1972

ite States atent Vose Att0rneyl(enwood Ross and Chester E. Flavin [54]COUNTERBALANCE AND LIFT SYSTEM FOR MOWING UNITS [72] Inventor: Robert W.'Vose, 1528 Piper Road, W. Springfield, Mass. 01089 Mar. 12, 1970complishing the several functions of counterbalancing, adjust- [22]Filed: ing, equalizing, damping, lifting, and stowing the individualunits of a mowing machine or lawnmower. An air charge in an accumulatorfunctions as the resilient counterbalancing element; adjustability isobtained by the alteration of the air pressure; equalization resultsfrom hydraulic distribution to lifting cylinders at each of the mowingunits; and oscillation is suppressed by damping restrictions in the hydtionally, a pump and valve combination in converts the system to liftthe moving units for transport an to elevate and stow same.

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INVENTOR. ROBERT w. VOSE BY 14 6 mm; 6 7270M ATTORNEYS.

CROSS-REFERENCE TO RELATED APPLICATION system for mowing units, samebeing a part of the invention described and claimed herein.

BACKGROUND OF THE INVENTION 1. Field of the Invention In the mowing ofgrass other than for purely agricultural purposes, evenness of cut andresulting appearance are of importance, and a wide variety of specialmachines have been developed for achieving these desiderata.

2. Description of the Prior Art In all but the smallest mowing machinesor lawnmowers, it is usual to provide a plurality of individual mowingunits and to guide these units from a tractive unit by linkages allowingthem limited freedom to follow the contour of the turf. It is alsocustomary to counterbalance a portion of the weight of these units bysuspension from the tractive unit in order to reduce frictional drag onthe machine and to minimize turf damage. Such counterbalancing has beenaccomplished in the past by use of spring mechanisms, and in most caseseach mowing unit has been provided with an individual spring and anadjusting means. The springs used have necessarily been heavy and bulkyto provide a reasonable constancy of counterbalancing action over theconsiderably travel allowed for following turf irregularities.

Additional mechanisms are used in larger machines to lift the mowingunits to a transport position, suitable for traversing driveways androads and for negotiating obstacles such as curbings. Still moremechanisms are provided in most machines to elevate and stow theoutboard mowing units which project beyond the tractive unit, enablingthe machine to be used on confined grounds and to be convenientlystored. These various mechanisms range from simple hooks and chains topower-driven hydraulic systems, according to the size and type ofmachine.

The multiplicity of mechanisms which have been enumerated results inundesirable complexity and cost. Difficulties in maintenance and repairare encountered, and operation may be awkward. In particular, theadjustment of counterbalancing springs is often enigmatic to an ordinaryoperator.

SUMMARY OF THE INVENTION The resilience of an air charge in anaccumulator is utilized, through hydraulic transmitting means, tocounterbalance all the mowing units of a mowing machine. A pump and avalve convert the hydraulic portion of the system to lift the mowingunits to a transport position and to a stowed position. Equalization ofcounterbalancing among the mowing units is assured, and simplificationand convenience are obtained as compared with the use of separatemechanisms for each of the several purposes and mowing units.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view, from thefront, of a left-side outboard mowing unit, together with a portion ofthe frame of the tractive unit from which it is guided andcounterbalanced. Also shown is the attaching link for a right sideoutboard unit, the latter being a mirror image of the left-side unit andnot shown. The complete machine includes a third or central mowing unit,also not shown, disposed rearwardly of the two outboard units andarranged to traverse the gap between them.

FIG. 2 is a front elevational view of the outboard unit in its mowingposition, with indications in phantom of the positions taken by the unitwhen lifted for transport and when stowed.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. I, thereis shown a mowing unit consisting of a frame 2 carrying by means ofbearings 3, a shaft 5 and a bladed reel 6. Reel 6 is driven throughshaft 5 by a pulley 7 and belt 8 from a suitable pulley on the tractiveunit, not shown, and its blades shear against a bed knife 9 mounted inframe 2. Frame 2 is pivoted by pins 10 to a link 12 which is in turnpivoted about an extension 18 ofa fame 20 of the mowing unit. By thismeans, the mowing unit is constrained to move generally with thetractive unit, but is allowed freedom to follow the contour of the turfover which it rides on a skid mounted below bed knife 9 and not visiblein the drawing. A second link 13 pivots about extension 18 and carries asecond mowing unit, not shown, oppositely disposed to the first unit.

A portion of the weight of the mowing unit is counterbalanced through alink 32 pivoted to crossmember 4 of frame 2 and to a bellcrank 34.Bellcrank 34 is pivoted at 22 to frame 20 of the tractive unit, andreceives the thrust of a single-acting hydraulic cylinder 40 which isanchored at 24 to frame 20. The head end of cylinder 40 is connected bya suitable hose and piping 42 through a valve and positive displacementpump arrangement 46 and 48 respectively to an accumulator 50.Accumulator 50 is partially filled with oil or other suitable liquid,and its remaining volume is charged with air under pressure. In accordwith standard practice, the accumulator is provided with connections forintroducing the air charge from an external source and for exhaustingthe charge, if desired, and with a pressure gauge and a relief valve,none of which features are shown. Piping 42 is provided with branches 43and with restrictions 44, whose respective functions will be explainedsubsequently.

With valve 46 open and pump 48 inactive, the pressure of the air chargein accumulator 50 is transmitted hydraulically to cylinder 40, causing athrust on bellcrank 34 and a tension in line 32. By manual alteration ofthe pressure of the air charge in the accumulator, the tension in link32 may be adjusted to counterbalance any desired portion of the weightof the mowing unit, 60 to percent being the workable range. As themowing unit rises and falls in following the turf contour, themechanical linkage, cylinder 40, and the hydraulic liquid movecorrespondingly. In accumulator 50, this motion is absorbed by theresilience of the air charge, and with a sufficient volume of air theremay be obtained a reasonably constant counterbalancing effect throughoutthe normal vertical travel ofthe mowing unit.

By closing valve 46 and actuating positive displacement pump 48, liquidis forced from accumulator 50 to cylinder 40, raising the mowing unitclear of the turf, as shown by position A in FIG. 2. This is designatedas the transport position, and is used in traversing driveways and roadsand in negotiating obstacles such as curbings.

With valve 46 still closed, pump 48 may be further actuated, Stop 14fastened to extension 18 of frame 20 prevents further angular travel oflink 12, and consequently the mowing unit is elevated about pins 10until it reaches the stowed position 8" of FIG. 2. In thisconfiguration, the overall expanse of the mowing machine is reduced forconvenience in storage.

From either the transport or stowed positions, the mowing unit may belowered to the working position by opening valve 46, and thecounterbalancing action of the system will be resumed automatically.Restriction 44 in piping 42 prevents sudden descent of the unit whichmight endanger personnel and equipment, and also furnishes damping tosuppress oscillation as disclosed in my above mentioned copendingapplicatron.

Piping branches 43 are provided in sufficient number for connection tosimilar counterbalancing arrangements on each of the mowing unitsincluded in the mowing machine, thereby providing for the hydraulicallyequalized counterbalancing of all such units. Operation of valve 46 andpump 48 will simultaneously lift or lower all units as desired. A unitwhich does not project outboard of the main tractive unit need not beelevated beyond the transport position (A of FIG. 2) and accordingly maybe restrained in that position by suitable stops while pump 48 continuesto elevate and stow the outboard units.

In large machines, particularly those having five or more mowing units,it may be desirable to be able to stow an outboard pair of units whileleaving the inboard unit or units in counterbalanced position formowing, thus adapting the machine to temporary use on restrictedgrounds. This may be accomplished by segregating the counterbalancecylinders of the outboard pair of units from the main piping system andserving them instead through a separate valve-and-pump combination fromthe main accumulator 50.

In small mowing machines, pump 48 may advantageously be operatedmanually, giving the operator direct control of the action. In largermachines, pump 48 may be power-operated, in which case it is necessaryto provide certain pressure relief valves and automatic shutoff devicesto prevent damage from overtravel, in accord with standard practice.

lclaim:

1. in a mowing machine having a tractive unit and a mowing unit, meansfor counterbalancing the mowing unit connected between the mowing unitand tractive unit and including an accumulator having a resilient chargeof compressed gas as its active element.

2. The means as set forth in claim 1, and including a hydraulictransmitting means acting between the accumulator and the mowing unit.

3. The means as set forth in claim 2, and including in the hydraulictransmitting means a valve and a pump arranged to convert the hydraulicmeans to furnish positive lifting of the mowing unit.

1. In a mowing machine having a tractive unit and a mowing unit, meansfor counterbalancing the mowing unit connected between the mowing unitand tractive unit and including an accumulator having a resilient chargeof compressed gas as its active element.
 2. The means as set forth inclaim 1, and including a hydraulic transmitting means acting between theaccumulator and the mowing unit.
 3. The means as set forth in claim 2,and including in the hydraulic transmitting means a valve and a pumparranged to convert the hydraulic means to furnish positive lifting ofthe mowing unit.